Android的一个Relative Layout的简单例子

public class ex07 extends Activity implements OnItemClickListener {
private final int WC = ViewGroup.LayoutParams.WRAP_CONTENT;
private String[] data = {" Item-1 ", " Item-2 ", " Item-3 "};
private TextView tv;
private String selection = "****";
private ArrayAdapter<String> adapter;
private boolean[] status = {false, false, false };
@Override
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
RelativeLayout r_layout = new RelativeLayout(this);
setContentView(r_layout);

LayoutInflater inflate = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);
//定义一个过滤器，用来处理布局的筛选
LinearLayout layout = (LinearLayout)inflate.inflate(R.layout.list, null);
RelativeLayout.LayoutParams param= new RelativeLayout.LayoutParams(175, WC);
layout.setId(1);
//定义了一个list布局，用来存放listview的布局
r_layout.addView(layout, param); //将list布局加入到relative类型布局中
tv = (TextView)layout.findViewById(R.id.text);//一个TextView
ListView lv = (ListView)layout.findViewById(R.id.list);//一个listview
lv.setBackgroundResource(R.drawable.bk_red);
adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_multiple_choice, data);
lv.setAdapter(adapter); lv.setItemsCanFocus(false);//将Adapter加入到listview中
lv.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);//多选模式
lv.setOnItemClickListener( this);

Button btn1 = new Button(this);
btn1.setBackgroundResource(R.drawable.bk_ok_exit);
btn1.setId(2); btn1.setText("OK"); btn1.setOnClickListener(listener);
param = new RelativeLayout.LayoutParams(60, WC);
param.addRule(RelativeLayout.RIGHT_OF, 1);
param.leftMargin = 15; param.topMargin = 20;
r_layout.addView(btn1, param);//将param用到了view之间的布局中
//将btn1这个view加入到layout中
//透過參數物件來敘述，按鈕寬60點，位於layout的右邊，相距15點，而且距離上方邊界20點。最後將btn1加入到r_layout裡

Button btn2 = new Button(this);
btn2.setBackgroundResource(R.drawable.bk_ok_exit);
btn2.setId(3); btn2.setText("Exit"); btn2.setOnClickListener(listener);
param = new RelativeLayout.LayoutParams(60, WC);
param.addRule(RelativeLayout.BELOW, 2);
param.addRule(RelativeLayout.ALIGN_LEFT, 2);
param.topMargin = 25;
r_layout.addView(btn2, param);
//将btn2加入到layout中
}
OnClickListener listener = new OnClickListener() {public void onClick(View v) {
if(v.getId() == 2){
String ss = "{";for(int i=0; i< adapter.getCount(); i++){if(status[i]) { ss += data[i]; ss += " "; }}
ss += "}";setTitle(ss);}
else if(v.getId() == 3) finish();}};
//针对不同的选项做出的判断
public void onItemClick(AdapterView<?> arg0, View v, int idx, long arg3) {
status[idx] = ! status[idx]; }}

很明显的看到在Relative的layout中的各个view在布局中的位置是通过parm来自行确定位置的

补充说明中

RelativeLayout r_layout = new RelativeLayout(this);
setContentView(r_layout);
// ………
LayoutInflater inflate = (LayoutInflater) getSystemService(
Context.LAYOUT_INFLATER_SERVICE);
LinearLayout layout = (LinearLayout)inflate.inflate(R.layout.list, null, null);
// ……….
tv = (TextView)layout.findViewById(R.id.text);

这样的一个过程，採用的佈局是r_layout，而不是layout，所以不能直接寫為：

tv = (TextView)findViewById(R.id.text);

反之，如果是：

RelativeLayout r_layout = new RelativeLayout(this);
setContentView(R.layout.list);
tv = (TextView)findViewById(R.id.text);

就對了。因為list.xml 是目前生效的佈局。

最后看看/res/layout/list.xml 的內容如下：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<TextView android:id="@+id/text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Hello World, ex07" />
<ListView android:id="@+id/list"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>